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中文摘要：
渭河流域位于我国半干旱—半湿润季风环境敏感地带,保存其黄土-土壤地层的木炭屑提供了全新世以来的野火历史和气候变化的记录。通过对甘肃合水马家塬（MJY）和陕西扶风蒋阳村（JYC）全新世黄土-土壤剖面的磁化率、TOC、木炭屑研究分析表明：末次冰期11500aBP之前,渭河流域气候干旱,自然野火频繁发生,荒漠草原植被从内蒙古南部扩展到渭河流域;全新世早期（11500～8500aBP）野火发生频率大大降低;全新世适宜期（8500～3100aBP）气候温暖湿润的森林草原或混交森林景观环境下野火发生几率明显下降,但不同地点人类活动引发的火灾存在区域差异。全新世晚期近3100a以来,气候向干旱化发展,加之人类土地利用活动加剧,生物量燃烧的规模大范围增加,人为引发火灾比自然发生火灾更为普遍,从而导致土地资源退化,造成渭河流域北部旱作农业衰退和游牧部落的入侵。1500aBP以后,野火发生频率大大降低,可能由于渭河流域南部荒地已开垦殆尽,农田人工景观已基本建立,北部半农半牧经济也已确立,不再进行大规模放火烧荒,因而木炭屑浓度大幅度减少。
英文摘要：
The Weihe River drainage is situated in semi-arid and sub-humid monsoon-sensitive areas in the north of China. Charcoal preserved in the loess-soil profile provided records of wildfire history and climatic changes during the late Holocene. Total organic carbon,magnetic susceptibility and charcoal analysis of two Holocene loess profiles in the study area have revealed the relationship between Holocene wildfire activity,human activity and climatic changes. The results show that the climate was arid and local wildfire occurred frequently during the late time of the last glacial period before 11 500 aBP when steppe vegetation expanded from the Inner Mongolian Plateau southerly over the Weihe River drainage. Conversely,wildfires were reduced during the early Holocene. During the Holocene climatic optimum between 8 500 and 3 100 aBP,natural wildfires were largely reduced. Pathogenic alteration to the accumulated dust processes was so active that forest-grassland formed under the humid-warm climate of the Holocene Megathermal. However,localized wildfires in connection with human activities frequently occurred in different patterns at the study sites. With the drier climate and more intensified historical land-use,human-set fires were more common than the natural fires. Very high levels of biomass burning and deteriorated land-use conditions caused a regional desertion by the arable farming communities and the invasion of nomads in the northern part of the Weihe River drainage during the last 3 100 years. After 1 500 aBP,the amount of charcoal sharply decreased and wildfire occurrence slowly disappeared,which may have resulted from totally cultivated land for farming and fully established agricultural landscape in the southern part of Weihe River drainage of the Loess Plateau; meanwhile,mixed agriculture of semi-cultivation and semi-animal husbandry was gradually developed in the northern part of the Weihe River drainage.
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